A paper machine or paper finishing machine passing through the nip, the surface contamination and / or damage of the detection method

A method for detecting contamination on or damage to a web-contacting face in a paper machine or a paper finishing machine, including the steps of detecting vibrations of the web-contacting face over a period of time by means of a plurality of detectors arranged in association with the machine and determining the location of the contamination on or damage to the web-contacting face based on the time the vibrations were detected.